This invention relates generally to a data transmission and reception system, and more particularly a data transmission device, a data reception device, a data transmission and reception system, a data transmission method and a parameter setting method for a data reception device.
In accordance with the development of digital data transmission techniques, digital satellite broadcasting systems based on the picture compression technique known as MPEG2 is finding practical application. FIG. 1 depicts the structure of an illustrative digital satellite broadcasting system based upon the MPEG2 picture compression technique convention. This illustrative digital satellite broadcasting system includes a satellite broadcasting station 210 having a broadcasting antenna 211 and a broadcasting satellite 220 for receiving broadcast signals sent from satellite broadcasting station 210 via broadcasting antenna 211. Broadcasting satellite 220 is also configured for retransmission of the received broadcast signals to satellite broadcasting receivers 230, which are installed in the premises of each service subscriber.
In the digital satellite broadcasting system depicted in FIG. 1, various programs furnished by the program purveyor are encoded by an MPEG encoder to form an MPEG transport stream (MPEG-TS). This MPEG-TS is then modulated for satellite broadcasting and is transmitted to broadcasting satellite 220. Broadcasting satellite 220 then in turn transmits the received MPEG-TS to each satellite broadcasting receiver 230 on the premises of each service subscriber.
Satellite broadcasting receiver 230 acts as a reception terminal. Such a reception terminal, known as an integrated receiver and decoder (IRD) or a set top box (STB), is installed in the premises of each service subscriber. A television receiver 240 and a video tape recorder 250 are connected to satellite broadcasting receiver 230.
FIG. 2 depicts a block diagram of satellite broadcasting receiver 230 of the illustrative digital satellite broadcasting system depicted in FIG. 1. Satellite broadcasting receiver 230 includes a station selection unit (tuner) 231, a demodulator 232, a data decoder 233, a descrambler 234, an MPEG decoder 235 and a video outputting signal processor 236.
During the operation of satellite broadcasting receiver 230, the user selects a desired channel to be viewed by using station selection unit (tuner) 231. The signals of the selected channel are demodulated to MPEG encoded digital signals by demodulator 232. The MPEG encoded demodulated digital signals are supplied to data decoder 233 and to descrambler 234.
Typically, the MPEG encoded digital signals are transmitted in scrambled form. Key decoding information for allowing descrambler 234 to descramble the MPEG encoded digital signal is furnished from the service purveyor to each subscriber on an IC card 237 or the like. Data decoder 233 furnishes the key decoding information supplied from IC card 237 to descrambler 234 for descrambling the MPEP encoded digital signal. Descrambler 234 then descrambles the signal, and outputs an unscrambled signal to MPEG Decoder 235. If the delivered MPEG encoded digital signal is not scrambled, descrambler 234 outputs the signal received from demodulator 232 to MPEG decoder 235 without performing any descrambling processing thereon.
After descrambling, the descrambled MPEG encoded digital signal is supplied to MPEG decoder 235 which decodes the descrambled MPEG digital signal and outputs a decoded signal to video outputting signal processor 236. The video outputting signal processor is formed of a video encoder, such as an NTSC encoder 361, a copy protection signal generator 362, an adder 363 and a D/A converter 364. Video encoder 361 converts the digital video signals furnished from MPEG decoder 235 into a pre-set standard television system format, such as NTSC system format, by way of example. The resulting formatted signal is converted by D/A converter 364 from digital data to an analog video signal in accordance with the pre-set television system standard. This standard format, analog video signal is then output from video outputting signal processor 236, and satellite broadcasting receiver 230 (FIG. 1) to television receiver 240 and/or video tape recorder 250.
The digital satellite broadcasting system may include a pay-per-view service, which includes charging the viewer a special fee to permit the viewing of a specified program. In general, if the subscriber selects a pay-per-view program from a program table, which is supplied via the satellite transmission procedure noted above, the program selection information is supplied over a telephone network, for example, from satellite broadcasting receiver 230 to the supervising company. This information may also be transmitted via broadcasting satellite 220, or other appropriate transmission methods. Upon receipt of a request to view a program, the key decoding information for decoding the program signal is sent to the individual satellite broadcasting receiver 230 of the subscriber via the satellite transmission procedure noted above. This decoding information is used by satellite broadcasting receiver 230 to decode the incoming program as noted above. The subscriber is charged for viewing the program at the same time the signal is supplied to the subscriber.
The pay-per-view program is transmitted having a configuration which, while permitting proper viewing of the program via television receiver 240, evades recording by video tape recorder (VTR) 250, by way of example, to ensure proper copyright protection of the transmitted program. To this end a copy protect signal for disabling picture recording is appended to the pay-per-view program. This copy protect signal may be of the type developed by Macrovision Corporation.
Typically, the digital satellite broadcasting system sends various additional data, along with video and audio data, such as the key decoding data for decoding a particular program, a program table, and parameters for instructing the receiving or processing hardware of program satellite broadcasting receiver 230. Data decoder 233 of satellite broadcasting receiver 230 detects whether a hardware parameter instructing the use of copy protection signal generator 362 of video outputting signal processor 236 is present. If this parameter is detected, the copy protection signal generator is turned on in order to generate the copy protect signal which is then added to the digital video signals by adder 363 pursuant to the pre-set standard television system format.
Referring next to FIG. 3, a specific example of data decoder 233 will be further described. Data decoder 233 comprises a 64-bit control code register 332, a control code analyzer 333 and an other data stream processor 334. The demodulated signal received from demodulator 232 is furnished via switch 331 to other data stream processor 334, which extracts information, such as a program table by way of example, to control the display of the program table. However, when a control code is detected in the signal received from demodulator 232, switch 331 is activated to direct the signal to 64-bit control code register 332. This control code, which typically is a 64-bit control code, is extracted from the demodulated signal and placed into control code register 332. The control code is analyzed by control code analyzer 333 in order to properly set the parameters for other hardware items of the system, and for on/off control of the copy protect signal.
Two formats normally are provided for the copy protect signal: a pseudo horizontal synchronization pulse or a color stripe.
As is shown in FIG. 4, the pseudo horizontal synchronization pulse copy protect signal system inserts a pseudo horizontal synchronization pulse into the vertical blanking period of a video signal, thereby inducing malfunction of the usual automatic gain control (AGC) circuit of a VTR. This deteriorates the picture level and quality of the image which is to be recorded to a practically intolerable level. Thus, in this manner, satisfactory picture recording is inhibited by the pseudo horizontal synchronization pulse copy protect signal.
As is shown in FIG. 5, the color stripe, copy protect signal system inverts the phase of four lines of the color burst signal every 20 lines on the screen. This induces color inversion during VTR reproduction, which in turn deteriorates the recorded picture level to a practically intolerable level. Hence, satisfactory picture recording is inhibited by the color stripe copy protect signal.
However, it is possible that the copy protect signal will not only disable picture recording, as described above, but also will affect the operation of the television receiver. Thus, there are occasions wherein a particular television receiver may be subject to interference from the copy protect signal. Such a situation is depicted, by way of example, in FIG. 6.
A system has been developed which is able to remove this interference from a particular television receiver by modifying the parameters of the copy protection signal generator or, alternatively, by turning off a part of the copy protect signal. For example, if the color stripe copy protect system, which inverts the phase of the color burst signal on four out of every 20 lines, causes interference in a particular television receiver, such interference can be diminished or eliminated by changing the number of lines of the color burst signal which are phase inverted from four lines to two lines.
As another example, television interference may be reduced by phase inverting not all but only part of each color burst signal. This example is shown in FIG. 7 wherein only half of the burst signal in each line is phase inverted. However, with this scheme, older hardware, which inverts the entire burst in four lines will not be able to generate this newer type of copy protect signal. Additionally, since the transmitted control code would contain instructions for generating this never type of copy protect signal, instructions for the older copy protect signals will not be sent so that the older hardware will not be instructed to generate cannot generate the older type of copy protect signals. Thus, the newer type of copy protect signal cannot be produced unless new hardware, including a new integrated circuit, is used. Since the older copy protection hardware requires the older transmitted copy protect signals, and the newer hardware requires the newer transmitted copy protect signals, the older hardware attempts to process the newer signal or if the newer hardware attempts to process the older signal, interference will result.
Therefore, it would be beneficial to provide a transmission system which allows for both old and new hardware to function without interference.